Mercury switch relay



Dec. 8, 1936. c. H. LARSON 2,053,609

MERCURY SWITCH RELAY Filed March 24, 1936 3 Sheets-Sheet 1 chie 2 M5076 Dec. 8, 1936. c. H. LARSON 2,063,609

MERCURY SWITCH RELAY Filed March 24, 1956 5 Shets-Sheet 3 m cadaa N g} 62/3070 J Q95.

Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE Adlake Company, a

corporation of Illinois Application March 24, 1936, Serial No. 70,602

6 Claims.

In electro-mechanical relays, it is common practice, and in fact absolutely necessary, to provide some means for establishing the proper air gap when the relay is energized, for otherwise the remanence in the iron circuit of the relay would cause relay failure. Ordinarily, a set screw of non-magnetic material is used to prevent the armature of electro-mechanical relays from making physical contact with the rest of the iron in circuit, the set screw being adjusted so that the total reluctance of the entire magnetic circuit is sufficiently high that when the relay coil is deenergized, the remanence in the iron circuit does not affect the opening of the relay.

In mercury switch relays of the type described in the Larson Patent 1,967,247, the problem is less difficult, because the thickness of the glass is in itself an air gap. However, in some mercury switches, where certainty of operation is of the m utmost importance, it is desirable to provide other safeguards against relay failure, due to remanence in the iron circuit. The principal object of this invention is to provide such other safeguards.

Further and other objects and advantages of 35 this invention will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawings, in

which Fig. l is a diagrammatic view of a flasher made 30 in accordance with this invention, the switch parts being shown in the position they assume just prior to the energization;

Fig. 2 is a perspective view of the control switch displacer;

3 Fig. 3 is a view similar to Fig. 1, but the switch parts are shown in the position they assume just prior to de-energization of the control switch;

Fig. 4 is a diagrammatic view of a portion of the magnetic circuit, with a portion of the lower 40 pole piece counterbored;

Fig. 5 shows a front contact switch associated with a magnetic circuit constructed in accordance with this invention;

Fig. 6 is a fragmentary view of a switch associated with a magnetic circuit in which both pole pieces are counterbored;

Fig. '7 is a rear perspective view showing the physical form of the flasher relay;

Fig. 8 is a vertical, sectional view taken on the line 8-8 of Fig. 7.

It will be understood that the embodiments of the invention shown in the drawings and the speciflc description which follows are for the purpose of disclosure only and should not be construed as imposing limitations on the appended claims except as may be required by the prior art.

THE (llccorr BREAKERS 1. Control switch The control switch 32 (Fig. 1) is a back contact switch and comprises a switch envelope 40, preferably of glass, through the bottom of which spaced electrodes 4| and 42 are sealed. The central electrode 4| is surrounded by an insulating sleeve 43, preferably of glass, for a portion of its length, and the exposed end of the electrode is bent over with its end 44 alongside the insulating sleeve 43. This is done to prevent the arc of making and breaking the circuit from taking place at the end of the insulating sleeve 45, which would eventually result in disintegration of the sleeve.

The switch envelope contains a quantity of mercury 45 which is adapted under certain conditions to bridge the electrodes 4| and 42.

The displacer 41 by its position within the switch envelope determines the level of the mercury. It comprises (Figs. 1 and 2) a sleeve 45 of magnetic material telescoped over a glass tube 49 closed at upper end except for a small opening 50 and open at its lower end. The upper end of the glass tube is packed with cotton 5|.

The control switch is, in this case, a self-acting intermittent circuit breaker in which the rate of gas flow through the cotton determines the time interval between the making and breaking of the electrical circuit through electrodes 4! and 42.

Guide washers 52 and 53 have three or more smoothly rounded lugs 54 and 55 lightly touching the walls of the switch envelope in the vertical movement of the displacer 41. The guide washers are held in place by springs 56 which also serve to protect the switch envelope from breakage during shipping, due to any motion of the displacer.

Before sealing off the switch envelope at 51, it is evacuated and all the metal parts are degassed. The switch is then filled with an inert gas (helium, hydrogen, helium hydride, or the like).

The displacer 41 of the control switch 32 is adapted to oscillate within the switch envelope at a predetermined rate of oscillation, and in Fig. l the parts are shown in the position which they assume just before the circuit through the electrodes 4| and 42 is closed. The mercury level on the outside of the displacer 41 is higher than the level on the inside of the displacer, this difference of mercury levels being due to a slight gas pressure differential. This gas pressure differential is equalized by the outward flow of gas through the cotton packing BI, and thence through the small opening 50 at the top of the displacer. This results in the rise of the mercury level within the displacer and the fall of the mercury level on the outside. When the mercury level inside rises sufilciently to contact the end 44 of the electrode 4i the circuit through the switch is closed and the relay coils H become energized. The displacer is then lifted to the position shown in Fig. 3 and draws up with it a column of mercury as shown. This again results in a gas pressure differential, between the gas on the inside of the displacer and that on the outside, but in this case the pressure is less on the inside of the displacer than on the outside, so that there results a flow of gas back into the displacer through the opening II and cotton packing 5i. As the gas pressure differential is equalized, the mercury level on the outside of the displacer rises and that on the in- 1.; coils ii and iron circuit I2.

side falls until the mercury level falls below the end 44 of the electrode 4|. This breaks the circuit and the relay coils 1i become de-energized and the displacer falls by gravity to the position shown in Fig. 1.

In Fig. 3, the control switch 32 is shown in the position just before the circuit between the spaced electrodes 4i and 42 is broken by the receding mercury column within the displacer.

The magnetic circuit generally designated 62 associated with switch 32 comprises the relay The iron circuit is closed except for an air gap '13, the air gap formed by the thickness of the switch envelope and counterbore 14 in the lower pole piece. The air gap formed by the counterbore 14 is so arranged that the lower end of the magnetic sleeve 48 of the displacer 41, in its downward movement, enters the counterbore 14 before the upper end '16 enters the air gap 13.

As a result, the danger of having the displacer suspended in a position somewhat above the normal tie-energized position, due to remanence in the iron circuit, is substantially eliminated.

2. Lamp circuit breaker The lamp circuit breaker 33 (Fig. 1) is similar in many respects to the physical appearance of control circuit breaker 32, but it functions somewhatdiil'erently. The switch comprises a switch envelope 80, through the bottom of which spaced electrodes 8i and 82 are sealed, a mercury fill 83 and a displacer 84.

The switch 33 is a fast acting back contact switch and the mercury fill 83 bridges the electrodes 8| and 82 when the relay coil H is deenergized and the displacer 84 is down under the action of gravity.

The displacer 84 comprises a magnetic sleeve 85 telescoped over an enlongated glass thimble 86 having a small opening 81 in its top wall. The glass thimble 86 and the magnetic sleeve 85 are held in proper relative position by springs 88, which also clamp the guide washers I9 and 90 to the sleeve 85.

In the de-energized position (Fig. l), the displacer 84 floats on the mercury 83 raising the level to bridge the electrodes BI and 82, completing the circuit to the signal lamp I90. When the relay coils H are energized, the displacer 84 is raised to the position shown in Fig. 3, causing the mercury level to fall below the exaoeaeoo posed end ll of electrode II and thuabreakina the circuit to the signal lamp ill.

The magnetic circuit associated with th switch 93 comprises a continuation of the iron circuit 12 and relay coils II. is similar to that associated with switch 82 except that the air gap 92 is smaller, having been partly closed by the addition of the iron sleeve 19 which tends to lower the pick up value of the switch. Like the iron circuit associated with switch 32, the lower pole piece is counterbored as indicated at 93. Again the counterboring is arranged so that the lower end 94 of the magnetic sleeve enters it before the upper end 98 en ters the air gap 92. This counterboring 99 assists in overcoming the eflect of remanence and substantially eliminates the possibility of switch failure due to residual magnetism.

Circuit breaker 94 normally functions as a front contact switch, but in case of relay failure, it functions as a back contact switch. The switch is similar in many respects with switches 32 and I! and in so far as the parts are alike, the same reference characters will be used. The switch comprises a switch envelope ll, spaced electrodes 91 and 99, a mercury fill 99 and a displacer 96. The displacer thimble I4 is packed with cotton 99 to retard the movement of mercury within the'displacer thimble.

When the coils Ii are energized, the displacer 96 is lifted completely out of the mercury, which allows any mercury within the thimble II to fall away from the displacer, and since the mercury fill in the envelope is sumcient to bridge the electrodes 91 and 98 when the displacer is raised (Fig. 3) the circuit through lamp III is closed.

When the coils II are de-energized, the displacer falls to the position shown in Fig. l, but before the time delay element 99 has permitted mercury to rise within the thimble a suiilcient amount to make contact with the tip 9i of the electrode 91, the coils II are again energized so that the displacer is lifted to the position shown in Fig. 3.

In case the power for the control circuit fails for any reason, leaving the coils ll de-energized, the front contact switch 34 acts as a back contact switch, for unless the coils ll pick up the displacer 96 within a given period of time, the mercury rises suihciently within the displacer to bridge the contacts 91 and 98.

It will be noticed that in case of relay failure, both signal lamps HH and I02 would be lighted and even if one signal lamp should be burned out there would be at least one signal lamp illuminated.

Tan Giacurrs 1. The control circuit The control circuit is shown in light lines and functions to intermittently energize the relay coils H. In case the flasher is used at a railroad crossing, the local circuit is placed into operation whenever a train enters a given section of track and short circuits the track relay Ill which includes a back contact switch Ill associated with the control circuit and a back contact switch I i2 associated with the lamp circuit. The control circuit in practice is ordinarily energized by a battery H9 and the control switch 32 and the relay coils H are connected in series with the battery Ill and the back contact switch i ii of the track relay. The circuit can be traced from the battery H3 through the conductor Ii 4, switch Ill, conductor iii, electrode 4i, meg- The iron circuit.

cury 46, electrode 42, conductors H5 and III, to the relay coils I I, and back to the battery through conductor II8.

This circuit makes the control switch 32 a self acting intermittent circuit breaker, the rate oi oscillation of which is determined by the rate of flow of gas through the time delay element 5|.

2. Lamp circuit The lamp circuit is shown in heavy lines and includes the lamp circuit breakers 33 and 34, lamps I00 and MI. the back contact switch II2 of the track relay H0 and the secondary coil I02 of the transformer I03 which in practice is ordinarily energized from a IIO volt alternating current line.

The lamp I00 is controlled by the circuit breaker 33 and the lamp IOI by the circuit breaker 34 and when the coils II are de-energized (as in Fig. l)' the circuit through the lamp I00 may be traced from the secondary coil I02 through the conductor I20, through the back contact switch II2, conductor I2I, lamp I00, conductor I22, electrode 8I, mercury 83, electrode 82, conductor I23, and through conductor I24 back to the secondary coil I02 of the transformer I03.

When the relay coils II are energized (as in Fig. 3), the circuit through the lamp IOI may be traced from the secondary coil I02 of the transformer I03 through the conductor I20, back contact switch II2, conductor I2I, lamp IOI, conductor I25, electrode 91, mercury 83, electrode 98, conductor I26 and back through conductor I24 to the secondary coil I02 of the transformer I03.

OPiraArroN Switch 32 functions as a self-acting intermittent circuit breaker controlling the intermittent energization of the relay coils 1|, which in turn actuate the lamp circuit breakers 33 and 34, one of which functions as a back contact relay and the other as a front contact relay. As long as the coils II are intermittently energized above a predetermined frequency, the lamps I00 and IN will be alternately lighted and the desired flashing signal indication will be obtained.

In case of failure of the control circuit (shown in light lines), the relay coils II become permanently de-energized, in which case both switches 33 and 34 act as back contact switches and both lamps I00 and IM would be lighted.

PHYSICAL Foam OF THE RELAY The relay is mounted on an L-shaped bracket I30 (Figs. '7 and 8) for support, which carries a plurality of relay coils II. the upper two being associated with a top pole piece I32, and the lower two being associated with a bottom pole piece I33. The relay coils 'II have iron cores I34, with external iron connectors I35 which are held in place against the coils II by the nuts I3I screwed to the threaded ends of the pole pieces I34. The pole pieces I32, I33, the iron cores I34 and external connectors I35 constitute the iron circuit I2.

The poles I32 and I33 have vertical alined apertures I35, I36 and I31 adapted to receive the control circuit breaker 32 and lamp circuit breakers 33 and 34, respectively.

The switches 32, 33 and 34 are adjustably mounted within these apertures. In the pole pieces I32 and I33 vertically alined holes I38 and I39 are drilled to hold adjusting rods I40. A spring clip I42 (best shown in Fig. 8) is fastened at one end around the base I43 of the mercury switch tube, and at the other end to the adjusting rod I by nuts I44 and I45 screwed to the end I45 of the rod. A spring I" interposed between a wear washer I48,and the nut I44 tends to force the rod downwardly and this is resisted by the nuts I49 and I50 which are screwed on the threaded end I5I. Cork washers I52 are provided between the lower nut I49 and the pole piece I32. This arrangement permits raising and lowering of the switches to a desired position and locking into place.

Cousraaaomro Pom Pmoas (a) Lower pole piece No attempt will be made to explain in detail the theory which is believed to account for the advantages achieved by counterboring, for at best, it would only be conjectural. Certain advantages. however, are known to exist when one or more of the pole pieces are counterbored in accordance with this invention.

Counterboring of the lower piece is particularly advantageous when the iron circuit is associated with a pull-up switch, such for example as switches 32, 33, 34, of the flasher relay. The counterbore I4 associated with the control switch 32 has the desirable effect of limiting the height to which the displacer rises within the envelope irrespective of the 'voltage applied to the coil II; of shortening the travel of the displacer and making the stroke more uniform for relatively large variances in the voltage applied to the coils, thereby producing a more uniform rate of flasher operation under the varying conditions of service; and of substantially limiting the possibility of switch failure due to remanence in the iron circuit by increasing the air gap at the lower pole piece when the effect of remanence is greatest in the vicinity of the upper pole piece.

The counterboring 93 of the lower pole piece for the switches 33 and 34 has much the same effect as the counterboring I4 for the switch 32. The principal advantage of the counterboring, however, for the switches 33 and 34 is to overcome the eifect of remanence in the iron circuit because the air gap 92 between the pole pieces is smaller than the air gap for the controlling switch 32. The position of the displacer 84 where the effect of remanence is greatest is shown in Fig. 4. Again, it will be observed that in this position, the lower portion of the displacer has entered the counterbore 93 which has the effect of minimizing the tendency of the displacer to remain in the position shown. There is also an advantage in limiting the distance to which the displacer may enter the upper pole piece.

The counterbore 93 associated with the switch 94 is quite important because the gas pressure created within the displacer when the coil is deenergized adds to the effect of remanence in tending to hold the displacer at a position corresponding to that shown in Fig. 4. The counterbore 93 substantially eliminates this tendency.

(17) Upper pole piece Although there is little tendency for a pulldown switch (normally called front contact switch) to fail because of remanence (this is due to the fact that the displacer is moved to the de-energized position by its own buoyancy rather than by gravity), there is nevertheless an advantage in counterboring the upper pole piece as shown at I52 in Fig. 5. In this case, the displacer generally designated III, is moved to the position shown in Fig. 5 by reason of the air gap I and when the coil H is de-energized, the buoyancy oi the displacer returns it to its normal raised position. Details of the switch itself are unimportant here and need not be specifically described except that a time delay element I" consisting of ceramic powder interposed between layers oi cotton I and I5! tends to draw up a column of mercury within the displacer when the coil is de-energized, thus increasing the weight of the displacer and opposing the force 01' buoyancy which is acting to restore the displacer to normal position. The counterbore Hi2 assists the mercury in buoying upthe displacer to its normal de-energized position.

(c) Counterboring both pole pieces In some special cases, it may be desirable to counterbore both pole pieces, as shown in Fig. 6, and the switch l5! associated with the pole pieces may be either a front or a back contact switch. Some desirable effects would also be obtained by counterboring the top pole piece from below rather than from above, as shown in Fig. 6.

i. In a mercury switch relay, a coil, an iron circuit associated with the coil including top and bottom pole pieces provided. with alined apertures, a mercury switch mounted in said apertures and comprising a switch enevelope, a mercury i i, spaced electrodes in the envelope, and a mercur; displace: movable in response to the =7 iron circuit for changing the condition of the electricai circuit through the electrodes, and means for minimizing the eiiect of residual magnetism in the iron circuit, said means including a counterbore in one of the pole pieces.

In a mercury switch relay, a coil, an iron circuit associated with the coil including top and bottom poie pieces provided with alined apertures, a mercury switch mounted in said apertures and comprising a switch envelope, a mercury fill, spaced electrodes in the envelope, and a mercury dispiacer movable in response to the iron circuit for changing the condition of the electrica: circuit through the electrodes, and means for minimizing the effect of residual magnetism in the iron circuit, said means including a counterbore in the lower pole piece.-

3. In a mercury switch relay, a coil, an iron circuit associated with the bottom pole pieces provided with alined apertures, a mercury switch mounted in said apertures and comprising a switch envelope, a mercury iill, spaced electrodes in the envelope, and a mercury displace: movable in response to the iron circuit for changing the condition of the electrical circuit through the electrodes, said lower pole piece being counterbored from the bottom to an extent that the lower portion of the dlsplacer enters the counterbore beiore the upper end leaves the upper pole piece when the displace:- is descending.

4. In a mercury switch relay, a coil, an iron circuit associated with the coil including top and bottom pole pieces provided with alined aperturu. a mercury switch mounted in said apertures and comprising a switch envelope, a mercury nu, spaced electrodes in the envelope, and a mercury displacer movable in response to the iron circuit for changing the condition oi the electrical circuit through the electrodes, and means for minimizing the eflect of residual magnetism in the iron circuit, said means including a counterbore in the upper pole piece.

5. In a mercury switch relay, a coil, an iron circuit associated with the coil including top and bottom pole pieces provided with alined apertures, a mercury switch mounted in said apertures and comprising a switch envelope, a mercury fill, spaced electrodes in the envelope, and a mercury displacer movable in response to the iron circuit for changing the condition oi the electrical circuit through the electrodes, said upper pole piece being counterbored from above for a substantial portion of its thickness.

6. In a mercury switch relay, a coil, an iron circuit associated with the coil including top and bottom pole pieces provided with alined apertures, a mercury switch mounted in said apertures and comprising a switch envelope, a mercury fill, spaced electrodes in the envelope, and a mercury displacer movable in response to the iron circuit for changing the condition of the electrical circuit through the electrodes, and means for minimizing the eiiect of residual magnetism in the iron circuit, said means including the counterboring of the top and bottom pole pieces for a substantial portion or their thickness.

CARL H. LARSON.

coiiincludlng top and 

